Fix erasure coded reads when a block is missing #86
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Kimahriman
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Resolves #74
We weren't handling the case where a shard in an erasure coded block was missing, only when the read from that shard failed. This cropped up because HDFS will consider a file "complete" when it has a minimal number of shards successfully written, not when all shards are available. So when reading immediately after writing, there may be some shards that haven't synced to the block/NameNode yet. This also represents what happens when a shard is actually unavailable due to a DataNode being down.